Aggregate function in an SQL update query?

Question

I'm trying to set the value in one table to the sum of the values in another table. Something along these lines:

UPDATE table1

SET field1 = SUM(table2.field2)

FROM table1

INNER JOIN table2 ON table1.field3 = table2.field3

GROUP BY table1.field3

Of course, as this stands, it won't work - SET doesn't support SUM and it doesn't support GROUP BY.

I should know this, but my mind's drawing a blank. What am I doing wrong?

Answer 1

Try using the code given below:

UPDATE t1

SET t1.field1 = t2.field2Sum

FROM table1 t1

INNER JOIN (select field3, sum(field2) as field2Sum

   from table2

  group by field3) as t2

on t2.field3 = t1.field3